To my understanding, the 1 tons or heavy duty trucks often got the steel cranks.
I don't think they were as common in the 1/2 tons although GM was never rigid on a lot of this during production.
I think they would substitute whatever they had to keep things moving through their plants.

For some reason, in the back of my mind, i have always thought 1/2 ton 350s were generally paired with 2 bolt mains and 3/4 ton or above 350s were paired with 4 bolt mains. But that may be an old wives’ tale... But this discussion begs another question - were the forged cranks always paired with 4 bolt mains and cast cranks with 2 bolt mains?

ALL of the 350's I have torn apart that have came out of trucks (approximately 8)... whether 1/2 ton or 3/4 ton have ALL been 4-bolt mains. ALL were cast iron cranks. No steel or forged cranks. Automatics or standard transmissions, 2WD or 4WD, didn't matter. I always figured trucks mainly got 4-bolts to account for the thrust applied though the crankshaft from the torque sent to the input shaft of the transmission from pulling or hauling heavy loads. But I might be wrong on that.

I love using vacuum gauges as part of the carb tuning process. I hook the gauge to the inside of my garbage can and leave it there.

Quote:

Originally Posted by Marv D

Remember Murphys 2nd law of mechanical relationships... "OPPOSING COMPONENTS ATTEMPTING TO OCCUPY THE SAME SPACE, AT THE SAME TIME, GENERALLY END UP OCCUPYING ADJOINING SPACE AT THE BOTTOM OF THE OIL PAN"

The original 350 in my 70 truck was a 2 bolt main. I threw rod through the side of the block at about 78,000 miles. I put a remanufactured long block in it with a 2 bolt main. The reman has about 100,000 on it. I know the previous two owners after me drove the crap out of it. I expect it to fail soon. With unleaded gas, everything in the later engines were upgraded. If it's an 80s engine I would run it till death or until it's too worn to perform. Then get the crate. But I wouldn't put any money into it. How many miles on it?

Some peole don't under stand the difference.Most 350 cranks had a thine seem line on the back of the crank where the fly wheel goes.The Hipo steel crank had a wide ground down kinda smooth line.So if you have a cranks with a small raised line that's a cast crank.The one with the wide grained smooth Is a steel crank .Here is a trip all of the Sm block 327 had steel cranks the large Jernal ones had ether one.Here is nother crazy one to add to the Mix If any of you have a 307 block put a 350 crank in it you now have a 327 large jernal 327 they put out some HP like in the 1966-67 nova's

Some peole don't under stand the difference.Most 350 cranks had a thine seem line on the back of the crank where the fly wheel goes.The Hipo steel crank had a wide ground down kinda smooth line.So if you have a cranks with a small raised line that's a cast crank.The one with the wide grained smooth Is a steel crank .Here is a trip all of the Sm block 327 had steel cranks the large Jernal ones had ether one.Here is nother crazy one to add to the Mix If any of you have a 307 block put a 350 crank in it you now have a 327 large jernal 327 they put out some HP like in the 1966-67 nova's

Actually, you put the 307 crank in the 350 block and that gives you a 327. I have a 4 bolt main 327 in my Jimmy. Large journal cast crank and 4 bolt main ‘72 truck block. My buddy had a 4 bolt main 327 he swapped into his ‘70 Z/28 and it was made, with all things, a steel crank from a 307 that was in a boat!

I'd think That a forged crank would be put in the manual 3/4 and up trucks as it see higher shock loads than a automatic transmission truck.
I know in the 96-00(02 in vans) the 3/4 tons and up got the 4 bolt block and the 1/2 tons 2 bolts.. both iirc are cast cranks..

I don't have the block numbers with me (I'm at work right now) but it came out saying HD truck. If I remember right, truck blocks from the late 60s and early 70s were always 4 bolt mains with a forged crank and even some mid power passenger 4 barrel cars had 4 bolt blocks and forged cranks.

Ok, well thanks for the info, I'll pop the pan down this spring time and try to get a peek.

The last time I saw a genuine factory forged crank was about 30 years ago. The 350 was out of a 69 Camaro. I've taken hundreds of 350s apart and never seen one since. They are a cast Nodular Iron. The forged cranks have about a 1'' wide band from the front main journal down to the number 1 and 3 rod journal. They also have a distinct ping when you tap them with a ball peen hammer with everything removed and standing up freely. I recently pulled out a 350 that was in my 69 GMC 1 ton dually. Pulled the pan off of that....not a forged crank. I was pretty sure it would have one, but .....nope

I just recently found that out. I had a peach of a 67 Chevelle with the original 4 barrel, double humper 327 and wondered if it was a 4 bolt block or not. Nobody seemed to know back then.

Here is some info on 327s from another post. There is no large journal 327s in 67 Chevelles and thus no 4 bolt mains.
***************
This addresses small journal 4-bolt 327s, but also 1968. Here are some of the highlights:

There is no such thing as a factory 327 4-bolt main. You can build one out a large journal block, but none were ever made factory. You will not find a single instance of anybody that can prove there ever was one. Lots of "I heard they did......" but no real evidence. There are pages on Google about this and not one of them I've seen can show any documentation that they exist.

There were no factory built cars with 4-bolt mains until 1969. No Corvettes, Z28s, or SS350 Camaros. If there were some blocks cast in '68, I believe they were for '69 model year vehicles.

http://www.ncrs.org/forums/archive/i...p/t-85289.html
I had not keyed in that there were no 4 bolts in '68 until recently. I had always assumed that the Z28s and SS350s in '68 got them. I knew that the '68 Corvettes did not. So that makes it even less likely that a 327 ever had 4-bolt mains because in '69 the only application for 327 was Camaros and B-bodies-and it was a more base engine as both had 350 performance engines available. By 1970 the 327 was gone and the 307 and 350 was it.
So '68 Z/28s and SS350 Camaros have 2-bolt mains.http://www.holisticpage.com/camaro/camaros/302.htm

Some LJ blocks cross over boundaries. For example, the 3956618 blocks were a 2-bolt for 68-69 327, a 4 bolt for 69 Z28, and 2 or 4 for 69 350. the famous 3970010 (and 3932386) is similar, but has no 68 applications. The raw casting had enough meat in the right places to machine it with either style cap.

No SJ block ever had 4-bolt mains. No documented 4-bolt LJ 327s were built. I could see a possibility in '69 with 0010 or 2386 block, but with all my searching I have yet to find anybody that can prove they have a legit one. And as we know, you could never prove it in a truck even if it did happen because the VIN derivative is not on the engine pad.

There are rumors of Massey-Ferguson combines with 327 4-bolts. The is no evidence this ever happed. Just another part of the legend.

There were industrial and marine engines from Chevy (and Ford and Chrysler). MF Combines did have Chevy 327s, but they were 2 bolt mains. MF combines did get 4-bolt SB engines, but they were 350s. I still maintain 2 things:
1-there is no such thing as a factory 327 with 4-bolt mains. Ever.
2-there were no small blocks with 4-bolt mains before the 1969 model year.

No need to apologize. Steel crank is the common term for a forged crank in car guy lingo. It's either steel or cast. Lots of opinions. I was always told the truck 350s were 4-bolt and the cranks were steel. My most recent experience is with the 327 I had rebuilt that was straight out of a '68 CST20 Custom Camper with a TH400. That has a forged steel crank. I have never had to rebuild a 350 in any of the trucks I've had. I've done earlier engines and 307s or bought 4-bolt 350 steel crank motors to build. I never cared what those came out of, but it's truck motors that I'd look for.

__________________
"BUILDING A BETTER WAY TO SERVE THE USA"......67/72......"The New Breed"

Here is some info on 327s from another post. There is no large journal 327s in 67 Chevelles and thus no 4 bolt mains.
***************
This addresses small journal 4-bolt 327s, but also 1968. Here are some of the highlights:

There is no such thing as a factory 327 4-bolt main. You can build one out a large journal block, but none were ever made factory. You will not find a single instance of anybody that can prove there ever was one. Lots of "I heard they did......" but no real evidence. There are pages on Google about this and not one of them I've seen can show any documentation that they exist.

There were no factory built cars with 4-bolt mains until 1969. No Corvettes, Z28s, or SS350 Camaros. If there were some blocks cast in '68, I believe they were for '69 model year vehicles.

http://www.ncrs.org/forums/archive/i...p/t-85289.html
I had not keyed in that there were no 4 bolts in '68 until recently. I had always assumed that the Z28s and SS350s in '68 got them. I knew that the '68 Corvettes did not. So that makes it even less likely that a 327 ever had 4-bolt mains because in '69 the only application for 327 was Camaros and B-bodies-and it was a more base engine as both had 350 performance engines available. By 1970 the 327 was gone and the 307 and 350 was it.
So '68 Z/28s and SS350 Camaros have 2-bolt mains.http://www.holisticpage.com/camaro/camaros/302.htm

Some LJ blocks cross over boundaries. For example, the 3956618 blocks were a 2-bolt for 68-69 327, a 4 bolt for 69 Z28, and 2 or 4 for 69 350. the famous 3970010 (and 3932386) is similar, but has no 68 applications. The raw casting had enough meat in the right places to machine it with either style cap.

No SJ block ever had 4-bolt mains. No documented 4-bolt LJ 327s were built. I could see a possibility in '69 with 0010 or 2386 block, but with all my searching I have yet to find anybody that can prove they have a legit one. And as we know, you could never prove it in a truck even if it did happen because the VIN derivative is not on the engine pad.

There are rumors of Massey-Ferguson combines with 327 4-bolts. The is no evidence this ever happed. Just another part of the legend.

There were industrial and marine engines from Chevy (and Ford and Chrysler). MF Combines did have Chevy 327s, but they were 2 bolt mains. MF combines did get 4-bolt SB engines, but they were 350s. I still maintain 2 things:
1-there is no such thing as a factory 327 with 4-bolt mains. Ever.
2-there were no small blocks with 4-bolt mains before the 1969 model year.

If there is any proof otherwise, I would love to see it.

I wondered about that thinking that maybe with 68 ushering in the large journal 327 cranks, maybe they made some 4 bolt 327 and/or with the new 350 in 68, maybe the HP versions had 4 bolt blocks. I guess not.

My HS buddy had a 69 Chevelle with a 300 hp engine and when he rebuilt it, he found it had a four bolt block with a forged crank. The engine rebuilder made a big deal out of it because it was only a 300 hp engine. He pinged the crank with a hammer and it rang like a bell... then he said, that's how you know if it's a forged crank or not. I never forgot it. I guess GM did some crazy stuff back then. He was also the guy who mentioned that truck 350s many times got a heavy duty bottom end... so that's why the original question.

No need to apologize. Steel crank is the common term for a forged crank in car guy lingo. It's either steel or cast. Lots of opinions. I was always told the truck 350s were 4-bolt and the cranks were steel. My most recent experience is with the 327 I had rebuilt that was straight out of a '68 CST20 Custom Camper with a TH400. That has a forged steel crank. I have never had to rebuild a 350 in any of the trucks I've had. I've done earlier engines and 307s or bought 4-bolt 350 steel crank motors to build. I never cared what those came out of, but it's truck motors that I'd look for.

Problem now is you can buy a china doll steel casted crank..
Have never used one but they are said to not be cast iron.